The 5 biggest takeaways from Mark Zuckerberg’s appearance before the Senate

Mark Zuckerberg made his highly anticipated debut before the Senate today during a marathon five-hour hearing before a joint session of the Commerce and Judiciary committees. Zuckerberg remained calm and level-headed throughout, and senators were mostly polite and deferential as they sought to understand how Facebook had inadvertently allowed the profiles of up to 87 million people to be collected by the political data-mining firm Cambridge Analytica.

In the weeks leading up to the hearing, Facebook made a series of announcements designed to demonstrate that it took the data leak seriously and was working to prevent it from happening again. Zuckerberg referred repeatedly today to these changes, which include making privacy shortcuts easier to find, restricting the data shared with developers when you log in using your Facebook account, labeling political ads and making them available for public inspection, and launching a bounty program to reward people who find examples of data misuse.

Facebook also sent Zuckerberg and his chief operating officer, Sheryl Sandberg, on a media tour to answer questions and hone their talking points. By the time today’s hearing began, Facebook had done what it could to ensure the day would feel light on news. Meanwhile, many senators still struggle to understand basic questions about how Facebook collects data and makes money. (Hint: not by selling that data to advertisers.)

Here are the five most notable developments from today’s hearings.

Zuckerberg had to confront Facebook’s monopoly power. When Sen. Lindsey Graham (R-SC) asked Zuckerberg to name his biggest competitor, Zuckerberg couldn’t name one. He was pressed repeatedly on Facebook’s large size, and at one point, he was asked whether Facebook was too powerful. Zuckerberg demurred. “It certainly doesn’t feel like that to me,” he said in response to Graham’s monopoly question. Senators do seem to be grappling with Facebook’s massive power in a way they haven’t before. But it’s not clear they have any coherent strategy to increase the amount of competition in the social media marketplace.